The former Manchester United and Arsenal forward has been sidelined since October with a hamstring injury.
Will Hughes is also back in the squad following a knee problem, but Ismaila Sarr (hamstring) and Kiko Femenia (knee) remain sidelined. Tom Cleverley (foot) has returned to training, but the game against Everton will come too soon for the midfielder.
Everton midfielder Jean-Philippe Gbamin has suffered a fresh setback in his recovery from a long-term groin problem which could require further surgery.
Gbamin and Andre Gomes are the only players missing for Everton for Saturday's trip, though Gomes is targeting a return against Arsenal on February 23 as his rapid recovery from a fracture dislocation of the ankle continues.
Watford provisional squad: Foster, Cathcart, Hughes, Doucoure, Capoue, Deulofeu, Kabasele, Deeney, Gomes, Dawson, Masina, Foulquier, Chalobah, Welbeck, Hughes, Pussetto, Pereyra, Quina, Gray, Success.
Everton provisional squad: Pickford, Stekelenburg, Coleman, Holgate, Keane, Mina, Baines, Digne, Delph, Schneiderlin, Sidibe, Sigurdsson, Iwobi, Davies, Walcott, Bernard, Calvert-Lewin, Kean, Niasse, Gordon, Gibson.